Occurrence and Geochemistry of the K-rich Brines in Deep-Seated Aquifers in the Sichuan Basin

Thursday, May 8, 2014: 4:00 p.m.
Xun Zhou , School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, China

Subsurface K-rich brines (K contents ranging from 1.5 to 53 g/L) are found in deep-seated aquifers in the Sichuan Basin of China. Most of the K-rich brines occur in the marine carbonate rocks of the Middle and Lower Triassic, Middle Cambrian and Sinian, and only small amounts of the K-rich brines are found in the continental Upper Triassic sandstone aquifers. The brine-bearing formations are at depth ranging from 300 to 4650 m and the brines are rich in anticlines and fault zones. The subsurface brines occur under a sealed state and do not receive any recharge. The brines have high TDS ranging from 80 to 388 g/L with relatively high concentrations of Br, I, Li, Sr, Ba, and B. The K-rick brines are mainly of Cl-Na and Cl-Na·Ca type. In particular, the PL4 well tapping the Middle Triassic brine-bearing carbonate rocks in the western part of the basin flows brines having TDS in the ranges of 348.392 to 377.27-387.78 g/L, which are close to those of the Yellow Sea water and the South China Sea water when evaporated to the stage of epsomite precipitation. K contents of the brines in the PL4 well range from 48.95 to 53.267-53.38 g/L and the B contents are as high as 4.994 g/L, which are much higher than those of the evaporated sea water at the stage of epsomite precipitation. Hydrogen and oxygen isotopes of the brines indicate that the K-rick brines in the carbonate rocks are of marine origin and those in the sandstone aquifers are of meteoric origin.

Xun Zhou, School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, China
Zhou Xun studied hydrogeology in Wuhan College of Geology from 1978 to 1982 as an undergraduate student, in China University of Geosciences (Beijing), from 1984 to 1987 as a graduate student, and from 1995 to 1998 as a doctoral candidate. He works in China University of Geosciences (Beijing) as a teacher and researcher in hydrogeology. His current research fields include groundwater in coastal zones, thermal groundwater (including hot springs), subsurface brines, groundwater circulation and its modeling.